[gaius]

more often it is because of the perceived ubiquity of Python 2.7 installs on the target user's computer

It’s not just “perceived”, it is actual reality e.g. on CentOS. If you need compatibility still the best option is 2, regardless.

[ptx]

In RHEL 8, Python 3 is finally the default Python version: https://developers.redhat.com/blog/2018/11/14/python-in-rhel...

[Wowfunhappy]

^^ Python 2.7 is also available by default on macOS, whereas you have to go out of your way to install Python 3.

[gaius]

... and Debian 9

I’m no Luddite but the simple fact today if you want to reliably deploy and can’t or don’t want to ship a container, Python 2 is the reality.

[rphlx]

FWIW deb9 installs both 3.5 and 2.7 by default.